THE ARTIODACTYL UNGULATES 203 



onid, as in the Kangaroos and more especially in the Baboon, 

 indicating a herbivorous diet. 



We can only glance briefly at the Hippopotamus Avhich again 

 possesses molars the bunodont cusps of which are obscured as 

 in the Pig by many secondary cuspules tending to convert 

 them into lophs. The crown of each molar presents therefore 

 a double trifoliate appearance. Such crowns are excellently 

 adapted for masticating the roots of succulent water weeds 

 torn out by the tusks of the animal. The dental formula is: 



l|, Cj,p|,m|. total 40. 



The incisors and the canines, the latter supported on 

 special bosses of bone, are all tusk-like in appearance and 

 possess persistently growing roots to compensate for the 

 marked attrition to which they are subjected in uprooting the 

 vegetation upon which the animal feeds. As in the Pig the 

 median upper incisors approximate at their tips and the lower 

 teeth are procumbent. Again, as in the Pig, the canines are 

 trihedral. The premolars, of which the first is lost early are 

 all simpler in form than the molars. All the cheek teeth are 

 subject to great wear from the large amount of sand and grit 

 among the food. The first molar which erupts considerably 

 before the others shows this wear strikingly. The structure of 

 the molar crowns has already been noted together with the 

 numerous secondary cingules and cuspules. The last lower 

 molar possesses a backwardly extended talonid. The rows of 

 cheek teeth are approximately parallel and the palate termi- 

 nates just behind the third molar. 



The elevated position of the ear-holes and orbits and the 

 dorsal situation of the nostrils in the Hippopotamus indicate 

 an aquatic habit, the animal floating entirely submerged save 

 for its ears, eyes and nose. 



